A built-in reaction device for removing nitrogen oxides from flue gas in a magnesium smelting industry

Abstract

The application provides a built-in reaction device for removing nitrogen oxides from flue gas in a magnesium smelting industry, mainly comprising a spraying nozzle, a spraying agent guide pipe, a protection cylinder, a temperature sensor, a flow sensor and a protection cylinder fixing frame. The overall device is installed at the center of a vertical preheater, the upper part of the device is fixedly connected with the upper end of a raw material bin of the vertical preheater, the protection cylinder penetrates through the upper end of the raw material bin to a discharge port of the vertical preheater, a plurality of spraying nozzles are installed at the end of the protection cylinder, the spraying nozzles can spray liquid and solid denitration reagents, nitrogen oxides in target objects can be effectively removed, and the end of the protection cylinder is provided with a temperature sensor and a flow sensor to monitor temperature and spraying flow changes. The existing device is provided with spraying nozzles outside the discharge port flue, which is inconvenient to install due to the irregular structure outside the discharge port, and high-temperature ores falling along the discharge edge will hinder the spraying of the spraying agent on the ores in the flue, affecting the removal effect of nitrogen oxides, and the temperature in the flue is not suitable for reaction. The device provided by the application can effectively solve the above problems, thereby achieving a better effect of removing nitrogen oxides.

Description

Technical Field

[0001] This invention relates to the technical field of environmental protection devices, and more particularly to a built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry. Background Technology

[0002] The calcination process in magnesium smelting focuses on high-efficiency, high-quality calcination of magnesium ore. In industrial applications, almost all magnesium smelting units use vertical preheaters as pretreatment devices for magnesium ore, connected to a rotary kiln via piping to achieve the ore calcination process. Control of pollutants such as nitrogen oxides (NOx) requires close adaptation to the process unit structure and site-specific conditions. In the vertical preheater, magnesium ore and flue gas exhibit a counter-current, multi-stage contact flow path, based on… Figure 1 The ore (material) falls mainly along the edge of the vertical preheater outlet by gravity, which is also the only usable reaction space in the nitrogen oxide reduction and removal technology.

[0003] Existing high-temperature reduction denitrification technology has the following problems:

[0004] 1. In magnesium smelting processes, most flues are also transitional components connecting vertical preheaters and rotary kilns. The flues are mainly octagonal, hexagonal, and circular flue connectors, with uneven shapes, which makes it very inconvenient to drill holes and install spray guns externally.

[0005] 2. Connecting flues generally share the common problems of short stroke and high temperature. Most connecting flues are less than two meters long, and the flues connect to the tail of the rotary kiln, where the temperature is generally above 1150℃. Therefore, they are not suitable for the use of NOx high-temperature reduction removal technology (suitable temperature: 850℃-1050℃, reaction residence time: more than 2s).

[0006] 3. After preheating, the ore is pushed into the discharge flue and then into the rotary kiln by a pusher. Due to gravity, the ore falls towards the edge of the flue. In existing denitrification processes, spray nozzles are installed outside the flue for spraying. However, the denitrifying agent is likely to be sprayed onto the ore falling near the edge of the flue. This results in most of the ore near the center of the flue not being sprayed with the denitrifying agent, leading to poor denitrification and hindering the implementation of the technology. Summary of the Invention

[0007] In view of the technical problems mentioned in the background section, this invention provides a built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry. This invention mainly utilizes the overall installation position of the spray nozzles, the positional combination between the individual spray nozzles, and their respective functions to more effectively remove the target nitrogen oxides.

[0008] The technical means employed in this invention are as follows:

[0009] An internal reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry includes: a spray nozzle, a spray agent conduit, a protective cylinder, a temperature sensor, a flow sensor, and a protective cylinder fixing frame;

[0010] The protective cylinder is fixed to the upper end of the raw material silo of the vertical preheater by the protective cylinder fixing frame. The protective cylinder extends from the upper end of the raw material silo of the vertical preheater from top to bottom to the discharge port of the vertical preheater. The protective cylinder is located at the axis of the vertical preheater and hangs down due to gravity.

[0011] The spray nozzles are evenly arranged at the lower end of the protective cylinder. The front end of the spray nozzle protrudes from the outer wall of the protective cylinder, so that the nozzle opening is fully exposed. The rear end of the spray nozzle is connected to a spray agent conduit. The spray agent conduit passes through the protective cylinder, and the tail end of the spray nozzle extends to the tail end of the protective cylinder. The tail end of the spray agent conduit is connected to the spray agent source.

[0012] Furthermore, the spray nozzles are evenly arranged in the flue gas duct at the outlet of the vertical preheater according to the effective reaction distance of the flue gas duct.

[0013] Furthermore, the number of spray nozzles is set based on the system's ammonia consumption, nitrogen oxide emissions, ammonia emissions, and compressed air, calculating the maximum number N of nozzles that meets the thermodynamic limits under operating conditions. max,热力学 N:

[0014]

[0015] Where, ρ gas A1 represents the average density of the flue gas; v represents the cross-sectional area of ​​the flue. max Indicates the maximum allowable flow velocity in the flue; c p ΔT represents the specific heat capacity of flue gas. max Indicates the maximum permissible temperature difference; η min h represents the lower limit of efficiency under the most unfavorable operating conditions. fg h represents the latent heat of water vaporization. fg =2260kJ / kg; Q pnozzle N represents the flow rate of a single nozzle. 冗余 Indicates the number of redundant nozzles.

[0016] Furthermore, the spray angle of the spray nozzle is set according to the spray type; the spray type includes: static liquid spray and solid spray.

[0017] Furthermore, when the spray type is static liquid spray, the liquid spray angle directly affects the water mist coverage area and residence time, thus affecting the cooling and reaction efficiency. Therefore, the static liquid spray angle θ1 is:

[0018] θ1=clip(k1×ln(v)+k2+k T×ΔT extreme ,θ min ,θ max );

[0019] Where v represents the flue gas velocity; k1 represents the logarithmic correction coefficient for the velocity; k2 represents the baseline angle value; k T Indicates the temperature extreme value correction factor; ΔT extreme θ represents the difference between the extreme high / low temperature and the preset temperature. min Indicates the minimum allowable angle for the nozzle mechanism; θ max Indicates the maximum allowable angle of the nozzle mechanically;

[0020] When the injection type is solid injection, to ensure sufficient reaction, the residence time of the solid injection in the flue should be >0.3s. Therefore, the solid injection angle θ2 is:

[0021]

[0022] Where θ0 represents the calibration reference angle; v represents the flue gas velocity; v0 represents the reference velocity, v0 = 5 m / s; d 颗粒 The average diameter of the drug particles is represented by d0; d0 represents the reference particle diameter, d0 = 50 μm; D 烟道 Indicates the diameter or width of the flue; D0 represents the standard flue dimension, D0 = 2m; k v k represents the flow rate correction factor. d k represents the particle diameter correction factor. D This indicates the correction factor for flue dimensions.

[0023] Furthermore, both the spray nozzle and the protective cylinder are made of corrosion-resistant and high-temperature-resistant materials.

[0024] Furthermore, a temperature sensor and a flow sensor are installed at the end of the protective cylinder to monitor changes in the temperature inside the flue and the flow rate of the spray.

[0025] Furthermore, the static liquid spray and the solid spray are arranged alternately, and the staggered distance between the static liquid spray and the solid spray is 5cm-10cm.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] This invention employs a reaction device with a built-in vertical preheater for nitrogen oxide removal. The vertical structure, with multi-layer feeding at the center of the flue, creates a suitable reaction atmosphere, solving the problem of poor performance caused by high reaction temperatures and short reaction paths in traditional reduction denitrification devices. Simultaneously, the vertical feeding at the center of the flue solves the problem of ore falling and preventing the sprayed reagent from effectively contacting the target material.

[0028] The device of this invention is based on the actual vertical preheater process of magnesium smelting, and flexibly constructs component sizes and layer distances, making it applicable to all magnesium smelting devices. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0031] Figure 2 This is a partial detailed view of the overall structure of the present invention.

[0032] Figure 3 This is a cross-sectional view of the detailed view of the present invention;

[0033] Among them, 1 is the spray nozzle; 2 is the spray agent conduit; 3 is the protective cylinder; 4 is the temperature sensor; 5 is the flow sensor; and 6 is the protective cylinder fixing bracket. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatuses.

[0036] like Figure 1As shown, the present invention provides a built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry, including: a spray nozzle 1, a spray agent conduit 2, a protective cylinder 3, a temperature sensor 4, a flow sensor 5, and a protective cylinder fixing frame 6.

[0037] The protective cylinder 3 is fixed to the upper end of the raw material silo of the vertical preheater by the protective cylinder fixing frame 6. The protective cylinder 3 extends from the upper end of the raw material silo of the vertical preheater from top to bottom to the discharge port of the vertical preheater. The protective cylinder 3 is located at the axis of the vertical preheater and hangs down due to gravity.

[0038] The spray nozzles 1 are evenly arranged at the lower end of the protective cylinder 3. The front end of the spray nozzle 1 extends through the outer wall of the protective cylinder 3, so that the spray outlet of the spray nozzle 1 can be fully exposed. The rear end of the spray nozzle 1 is connected to the spray agent conduit 2. The spray agent conduit 2 passes through the protective cylinder 3, and the tail end of the spray nozzle extends to the tail end of the protective cylinder 3. The tail end of the spray agent conduit 2 is connected to the spray agent source.

[0039] In this application, as a preferred embodiment, the spray nozzles are evenly arranged in the flue gas duct at the outlet of the vertical preheater according to the effective reaction distance of the flue gas duct. In this application, the number of spray nozzles 1 is set based on the system's ammonia consumption, nitrogen oxide emissions, ammonia emissions, and compressed air, calculating the maximum number N of nozzles that meets the thermodynamic limits under operating conditions. max,热力学 N:

[0040]

[0041] Where, ρ gas A1 represents the average density of the flue gas; v represents the cross-sectional area of ​​the flue. max Indicates the maximum allowable flow velocity in the flue; c p ΔT represents the specific heat capacity of flue gas. max Indicates the maximum permissible temperature difference; η min h represents the lower limit of efficiency under the most unfavorable operating conditions. fg h represents the latent heat of water vaporization. fg =2260kJ / kg; Q pnozzle N represents the flow rate of a single nozzle. 冗余 Indicates the number of redundant nozzles.

[0042] Furthermore, as a preferred embodiment, the spray angle of the spray nozzle 1 is set according to the spray type; the spray type includes: static liquid spray and solid spray. The static liquid spray and the solid spray are arranged alternately, and the staggered distance between the static liquid spray and the solid spray is 5cm-10cm.

[0043] When the spray type is static liquid spray, the liquid spray angle directly affects the water mist coverage and residence time, thus affecting the cooling and reaction efficiency. Therefore, the static liquid spray angle θ1 is:

[0044] θ1=clip(k1×ln(v)+k2+k T ×ΔT extreme ,θ min ,θ max );

[0045] Where v represents the flue gas velocity; k1 represents the logarithmic correction coefficient for the velocity; k2 represents the baseline angle value; k T Indicates the temperature extreme value correction factor; ΔT extreme θ represents the difference between the extreme high / low temperature and the preset temperature. min Indicates the minimum allowable angle for the nozzle mechanism; θ max Indicates the maximum allowable angle of the nozzle mechanically;

[0046] When the injection type is solid injection, to ensure sufficient reaction, the residence time of the solid injection in the flue should be >0.3s. Therefore, the solid injection angle θ2 is:

[0047]

[0048] Where θ0 represents the calibration reference angle; v represents the flue gas velocity; v0 represents the reference velocity, v0 = 5 m / s; d 颗粒 The average diameter of the drug particles is represented by d0; d0 represents the reference particle diameter, d0 = 50 μm; D 烟道 Indicates the diameter or width of the flue; D0 represents the standard flue dimension, D0 = 2m; k v k represents the flow rate correction factor. d k represents the particle diameter correction factor. D This indicates the correction factor for flue dimensions.

[0049] Preferably, both the spray nozzle 1 and the protective cylinder 3 are made of corrosion-resistant and high-temperature-resistant materials. A temperature sensor 4 and a flow sensor 5 are installed at the end of the protective cylinder 3 to monitor changes in the temperature inside the flue and the spray flow rate.

[0050] Example 1

[0051] In a magnesium smelting enterprise in northern Shaanxi, the initial NOx emission concentration was 550 mg / m³, the kiln tail temperature was 1220℃, and the effective reaction distance in the flue was 0.6 meters. SNCR and PNCR denitrification technologies could not be used. In this application, a nitrogen oxide removal device with a built-in vertical preheater was installed. The protective cylinder was 6.6 meters long, and three layers of spray nozzles were spaced 0.2 meters apart. First, liquid spray agent was sprayed into the kiln tail through the spray layer (a spray rate of approximately 800 L / h was used as a reference). After one hour of equilibrium, the oxygen content at the kiln tail decreased (from 10.5% to below 9.5%), the humidity increased (from 3% to above 5.0%), and the kiln tail temperature dropped from 1220℃ to 1180℃. Low-concentration denitrification agent was then added in both solid and liquid forms (a solid feed rate of 20 kg / h and a liquid feed rate of 2% urea were used as a reference), allowing a certain equilibrium time (approximately half an hour). Under this process, NOx emissions are 100-280 mg / m³. 3 Fluctuations, with a mean of 240 mg / m³ 3 Furthermore, both the peak and average sulfur dioxide emissions have been significantly reduced (with a reduction rate of over 50% as a reference).

[0052] Example 2

[0053] At a magnesium smelting enterprise in northern Shaanxi, the initial NOx emission concentration is 500 mg / m³, the kiln tail temperature is 1200℃, the effective reaction distance in the flue is 2 meters, and the injection point temperature is 1160℃. Therefore, denitrification technologies such as SNCR and PNCR cannot be used. In this application, a built-in vertical preheater nitrogen oxide removal device and reaction unit are installed. The protective cylinder is 8.8 meters long, and there are four layers of spray nozzles spaced 0.4 meters apart. First, liquid spray agent is injected into the kiln tail through the spray layer (a spray rate of approximately 500 L / h is used as a reference). After 0.5 hours of equilibrium, the oxygen content at the kiln tail decreases (from 10.0% to 9.2% is used as a reference), the humidity increases (from 2.8% to 4.0% is used as a reference), and the kiln tail temperature drops from 1200℃ to 1190℃. A low concentration of denitrification agent is then added in both solid and liquid forms (based on a solid feed rate of 20 kg / h and a liquid feed rate of 1.5% urea as a reference), allowing a certain equilibrium time (approximately half an hour). Under this process, NOx emissions are stabilized at 250 mg / m³. 3 Furthermore, both the peak and average sulfur dioxide emissions have been significantly reduced (with a reduction rate of over 50% as a reference).

[0054] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0055] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0056] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0057] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0058] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0059] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry, characterized in that, include: Spray nozzle (1), spray agent conduit (2), protective cylinder (3), temperature sensor (4), flow sensor (5), and protective cylinder fixing bracket (6); The protective cylinder (3) is fixed to the upper end of the raw material silo of the vertical preheater by the protective cylinder fixing frame (6). The protective cylinder (3) extends from the upper end of the raw material silo of the vertical preheater from top to bottom to the discharge port of the vertical preheater. The protective cylinder (3) is located at the axis of the vertical preheater and hangs down due to gravity. The spray nozzles (1) are evenly arranged at the lower end of the protective cylinder (3). The front end of the spray nozzles (1) protrudes from the outer wall of the protective cylinder (3) so that the nozzle opening of the spray nozzles (1) can be fully exposed. The rear end of the spray nozzles (1) is connected to the spray agent conduit (2). The spray agent conduit (2) passes through the protective cylinder (3), and the tail end of the spray nozzles extends to the tail end of the protective cylinder (3). The tail end of the spray agent conduit (2) is connected to the spray agent source.

2. The built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry according to claim 1, characterized in that, The spray nozzles (1) are evenly arranged in the flue of the vertical preheater outlet according to the effective reaction distance of the flue.

3. The built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry according to claim 1 or 2, characterized in that, The number of spray nozzles (1) is set based on the system's ammonia consumption, nitrogen oxide emissions, ammonia emissions, and compressed air, calculating the maximum number N of nozzles that meets the thermodynamic limits under operating conditions. max,热力学 N: Where, ρ gas A1 represents the average density of the flue gas; v represents the cross-sectional area of ​​the flue. max Indicates the maximum allowable flow velocity in the flue; c p ΔT represents the specific heat capacity of flue gas. max Indicates the maximum permissible temperature difference; η min h represents the lower limit of efficiency under the most unfavorable operating conditions. fg h represents the latent heat of water vaporization. fg =2260kJ / kg; Q pnozzle N represents the flow rate of a single nozzle. 冗余 Indicates the number of redundant nozzles.

4. The built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry according to any one of claims 1-3, characterized in that, The spray angle of the spray nozzle (1) is set according to the spray type; the spray type includes: static liquid spray and solid spray.

5. The method for removing nitrogen oxides in the magnesium smelting industry according to claim 4, characterized in that, When the spray type is static liquid spray, the liquid spray angle directly affects the water mist coverage and residence time, thus affecting the cooling and reaction efficiency. Therefore, the static liquid spray angle θ1 is: θ1=clip(k1×ln(v)+k2+k T ×ΔT extTeme ,i min ,i max ); Where v represents the flue gas velocity; k1 represents the logarithmic correction coefficient for the velocity; k2 represents the baseline angle value; k T Indicates the temperature extreme value correction factor; ΔT extreme θ represents the difference between the extreme high / low temperature and the preset temperature. min Indicates the minimum allowable angle for the nozzle mechanism; θ max Indicates the maximum allowable angle of the nozzle mechanically; When the injection type is solid injection, to ensure sufficient reaction, the residence time of the solid injection in the flue should be >0.3s. Therefore, the solid injection angle θ2 is: Where θ0 represents the calibration reference angle; v represents the flue gas velocity; v0 represents the reference velocity, v0 = 5 m / s; d 颗粒 The average diameter of the drug particles is represented by d0; d0 represents the reference particle diameter, d0 = 50 μm; D 烟道 Indicates the diameter or width of the flue; D0 represents the standard flue dimension, D0 = 2m; k v k represents the flow rate correction factor. d k represents the particle diameter correction factor. D This indicates the correction factor for flue dimensions.

6. The built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry according to claim 1, characterized in that, Both the spray nozzle (1) and the protective cylinder (3) are made of corrosion-resistant and high-temperature resistant materials.

7. The built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry according to claim 1, characterized in that, The protective cylinder (3) is equipped with a temperature sensor (4) and a flow sensor (5) at its end to monitor the temperature and flow rate changes in the flue.

8. The built-in reaction device for removing nitrogen oxides from flue gas in the magnesium smelting industry according to claim 4, characterized in that, The static liquid spray and the solid spray are arranged alternately, and the staggered distance between the static liquid spray and the solid spray is 5cm-10cm.

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